1. Field of the Invention
The present invention relates to a CD (Compact Disk) player, and more particularly, to a CD player capable of playing back a partially recorded, additionally recordable CD-R (CD Recordable).
2. Description of the Related Art
The CD is well known as a recording medium to record acoustic information or the like. The CD has a lead-in area LIA where index information of recorded information is recorded, a program area PA where actual musical information is recorded, and a lead-out area LOA indicating the end of the program area PA, formed thereon in the named order from the inner periphery of the disk, as shown in FIG. 1(a). Those areas LIA, PA and LOA as a whole are called an information area. A signal to be recorded is a digital signal modulated by EFM (Eight to Fourteen Modulation), and includes a main code (main information) such as musical information, and a sub code such as a time code (time information). Index information called TOC (Table Of Contents) is recorded in the lead-in area LIA, and the total number of recorded information pieces (e.g., the total number of musical pieces), the total program time (e.g., the total playing time), etc. are recorded as a sub code also in that area LIA. Musical information or the like is recorded as a main code in the program area PA. A track number (TNO) indicating the number of each piece of recorded information (e.g., the music number), the program time (P-TIME) from the beginning of the track, such as the playing time of the music piece, the total program time (A-TIME) measured from the first track number (=1), such as the total playing time, etc. are recorded in the Q channel of the sub code in the program area PA. In the lead-out area LOA is recorded a lead-out code indicating the lead-out area.
In a CD player that plays back the above CD, when the CD is set, a pickup is moved to a predetermined position (home position), a setup operation is then performed to rotate the CD to make it ready for information reading therefrom, and TOC information is read from the lead-in area upon completion of the setup operation. In reading the TOC information, however, the TOC information may not be acquired due to some scratches on the disk. In such a case, information in the program area is to be reproduced without TOC information. To accomplish this reproduction, conventionally, it is discriminated whether the disk is a "normal CD with TOC" or "normal CD without TOC" based on the result of reading the TOC information, and the information on the discrimination result is stored as disk discrimination information.
FIG. 2 shows a flowchart of a process for reading TOC information in the conventional CD player. It is seen from the flowchart that conventionally, the information area is searched first for the lead-in area for a given period of time (steps S51, S52 and S53). If the lead-in area cannot be detected when the time is out, i.e., the TOC information cannot be read out, it is considered that the disk is a "normal CD without TOC" and the information to that effect is stored (step S57). When the lead In area is detected, the TOC information is read until the reading is complete or the time is out (steps S54, S55 and S56). When the time is out, or the TOC information cannot be read, the disk is considered as a "normal CD without TOC" and the information to that effect is stored (step S57). When the reading is complete, on the other hand, the disk is considered as a "normal CD with TOC" and the information to that effect is stored (step S58). The disk discrimination information thus acquired and stored will be used in later processes such as information searching.
While a CD having the above-described recording format is a read-only recording medium, an additionally recordable CD-R having the same format as the CDs has been developed recently. This CD-R recording format standard is standardized into a so-called "Orange Book", and conforms to the CD format standard (called a "red book"). The CD-R disks are classified into the following three types as shown in FIG. 1(b) to FIG. 1(d) depending on the recording status.
FIG. 1(b) shows a section of a blank or unrecorded CD-R disk where no information has been recorded yet. FIG. 1(c) shows a section of a partially recorded CD-R disk (hereinafter referred to as "PRD") where information is partially written. FIG. 1(d) shows a section of a finalized CD-R disk for which recording is complete and which has finally been formatted in nearly the same format as CDs.
As illustrated in FIG. 1(b) to FIG. 1(d), the lead-in area LIA, program area PA and lead-out area LOA are also formatted on each CD-R in the same manner as that of CDs.
A pregroove is formed on the recording track of a CD-R, and it is wobbled by a frequency that is acquired through FM modulation of a carrier with data indicating the absolute time information (ATIP: Absolute Time In Pregroove). In a CD-R recording and playback apparatus, the tracking control and spindle control are performed according to the pregroove so that information is recorded on and read from a blank disk as well as a PRD. A PMA (Program Memory Area) as a temporary TOC area to store the recording history of recorded information is provided on the PRD at the inner periphery side of an area I that is reserved for the lead-in area LIA as indicated in FIG. 1(c). In this PMA the following three types of information are recorded. The first information includes the start and end addresses of information recorded in the program area, which are recorded in the same format as TOC information that is recorded in the lead-in area. The second type is disk identification information (optional) which may be 6-digit numeral information to identify a disk as needed. The third type is skip command information and skip release information, which are associated with a command to skip the recorded information piece (track) by piece or part of each piece (track) of the recorded information (time designatable in the latter case) at the time of playing back the disk. The reason for recording such information as temporary TOC in the PMA is that since information is writable in the remaining program area PA on the PRD, TOC information cannot be recorded in the lead-in area LIA until the finalization of recording is instructed finally.
In a PRD, no information is written in an area I for the lead-in area LIA and an area O for the lead-out area LOA. Therefore, those areas remain in a mirror-finished state. When a command for finalization is given, the CD-R recording apparatus records predetermined information and TOC information recorded in the PMA as a sub code in the area I for the lead-in area LIA, and records a predetermined lead-out code indicating the lead-out area LOA in the area O for the lead-out area LOA in order to provide the same format as that of CDs at last. This allows the conventional CD player to play back the finalized CD-R.
While the conventional CD player is capable of playing back a finalized CD-R, it cannot reproduce reproducible information from a PRD though that information is stored in the program area PA. To describe in detail, it is so because of the following reasons. Although a PRD has TOC information recorded in the PMA provided on the inner periphery side of the lead-in area, the conventional CD player is equipped with no mechanism to access that PMA. In addition, the area I for the lead-in area LIA and the area O for the lead-out area LOA remain mirror-finished and the conventional CD player is not designed to perform the proper control on information reading from such areas so that runaway of the servo system may occur in reading information from those areas.
As a solution to this problem, like the CD-R recording and playback apparatus, the CD player may be equipped with the mechanism to access the PMA and some means to read the pregroove and perform the tracking and spindle controls. The provision of such means only for the PRD is not cost effective.
Prior to the reproduction of recorded information, the conventional CD player moves the pickup to the position corresponding to a predetermined home position on a CD in accordance with the recording format of the CD and performs a setup operation such as pull-in of a servo system. This home position is set near the boundary between the lead-in area LIA and program area PA for the conventional CD player.
However, the home position on the CD is likely to deviate depending on the precision of the mechanism of the CD player and the eccentricity of the CD. The predetermined physical home position of the pickup may not therefore correspond to the predetermined home position on the CD. With a PRD set in the conventional CD player, since no information is yet recorded in the area I for the lead-in area LIA which remains mirror-finished, the setup operation cannot be carried out when the physical home position of the pickup enters this area I. Even if the setup operation is tried again (setup retry), the physical home position of the pickup is very likely to enter the area I for the lead-in area LIA again, making it unlikely to properly finish the setup operation. Even if some information has been recorded on the CD-R, it is considered that the disk is set with the back side facing the pickup, thus terminating the reproducing operation or rejecting that disk (first problem).
There is a demand for the development of a CD player which can reproduce information from the program area simply with alteration on the control system for PRDs in order to widen the applicability of CD-Rs. As mentioned earlier, the read-only CD and the PRD have different disk formats. Therefore, the conventional CD player cannot play back a PRD by the same control as employed for CDs and needs different control. With the use of the above-described disk discrimination in the conventional CD player that determines the type of the disk depending on whether or not it has "TOC", the PRD is discriminated as a "normal CD without TOC" and this discrimination is insufficient to reproduce information from the program area of the PRD (second problem).